#include <stdio.h>
#include <math.h>
void main()
{
    int i,count;
    printf("There are invertable primes with 4 digits:\n");
    for(count=0,i=1001;i<9999;i+=2)
        if(num(i))
            printf(count%9?"%3d:%3d":"%3d:%3d\n",++count,i);
    printf("\n");
}
int num(int number)
{
    int j,i;
    if(!ok (number))
        return  0;
        for(i=number,j=0;i>0;i/=10)
            j=j*10+i%10;
        if(number<j)
            if(!ok(j))
                return 0;
            else
                return 1;
        else
            return 0;
}
int ok(int number)
{
    int i,j;
    if(number%2==0)
        return 0;
    j=sqrt((double)number)+1;
    for(i=3;i<=j;i+=2)
        if(number%i==0)
            return 0;
    return 1;
}
